1. Technical Field of the Invention
The present invention generally relates to an air cleaner, and more specifically, relates to an air cleaner installed within a ceiling of a clean room used for manufacturing elements or devices such as semiconductor or liquid crystal arrangements, wherein the air cleaner has a vane-wheel capable of improving a fan efficiency and capable of decreasing a noise and a vibration.
2. Description of Related Art
An example of a construction of an air cleaner in a related art is explained referring to FIGS. 20-22. As is disclosed in FIG. 20, the air cleaner 20 in the related art has a fan including a vane-wheel 10 and a motor 6 for rotating the vane-wheel 10, a filter 24 and a housing 21 for accommodating the fan and the filter 24. A motor base 7 supports the motor 6 in the housing 21. The housing 21 has an air inlet 26 at its upper plate, and has an opening at its bottom portion for installing the filter 24. A filter frame 28 is disposed so as to surround the outer periphery of the filter 24. The frame 28 has a gasket 29 at its bottom. A pressurizing chamber 22 is formed inside the housing 21 in an upper stream side of the filter 24.
The vane-wheel 10 is directly connected to a rotational shaft of the motor 6 through a boss 5, and is driven rotatively by the motor 6 so as to take in air from the air inlet 26. When the vane-wheel 10 rotates, the air from the air inlet 26 is sucked through a sucking port 10a of the vane-wheel 10 and is blown out from a blowing port 10b of the vane-wheel 10. The air blown out from the blowing port 10b is supplied to the pressurizing chamber 22 for increasing a static pressure thereof and is then supplied to the filter 24. The filter 24 purifies the air by removing such small particles having diameters as small as 0.1 micrometers. At the air inlet 26, a bell mouth 26a is provided on the opposite side of the sucking port 10a in order to smooth a flow of the air which is sucked.
As disclosed in FIGS. 21 and 22, the vane-wheel has a base plate 2, a shroud 1, and a plurality of vanes 3. Each vane 3 is made of metal sheet such as alminium or stainless steel and is formed to have a curved surface. The vane 3 has a shape of a simple curved plate or complicated three-dimensional shape. The vane 3 has a plurality of tongues 3a at both sides facing respectively to the shroud 1 and the base plate 2. The shroud 1 and the base plate 2 have slots 1d and 2b, respectively, where the tongues 3a are inserted and secured. The shroud 1 has recessed portions 1c, where one side of each vane facing to the shroud 1 is engaged.
A problem in the related art is deterioration of the fan efficiency and increase of noise. More particularly, since each vane 3 is formed into a plate with a curved surface, a front end (an end facing to the sucking port 10a) 3f of the vane 3 has an edge. When the fan rotates, the edge induces turbulence of air, which results in increase of noise and pressure loss, and thereby an efficiency of the fan is deteriorated.
Another problem in the related art is increase of pressure loss along the surface of the vanes. That is, since the air cleaner in the related art is designed to obtain required air pressure by increasing the numbers of vanes, an area where an air flow that flows through the vane-wheel contacts the surfaces of the vanes increases. This increases friction between the air and the surfaces of the vanes, which results in increase of pressure loss along the surface of the vanes.
A further problem in the related art is occurrence of undesirable vibration or noise due to imbalance of the vane-wheel. More specifically, in the related art, the base plate 2 of the vane-wheel 10 has a flat portion 2a extending to its outer periphery. The shroud 1 of the vane-wheel 10 also has a flat portion at its outer periphery 1a. In order to prevent undesirable vibration or noise, a U-shaped balance weight 70 is attached at least to either one of the flat portions of the base plate 2 or the shroud 1. The balance weight 70 has arms 70a forming parallel sides of the U-shape, and the balance weight 70 squeezes the outer periphery of the base plate 2 or the shroud 1 with arms 70a. The balance weight 70 is fixed just by elastic forces of the arms 70a or just by a friction between the arm 70a and the surface of the base plate 2, or that between the arm 70a and the surface of the shroud 1. Such minimal securing approach allows displacement of the balance weight 70 by an unexpected external force in tangential direction at the time of handling the vane-wheel 10, eventually resulting in occurrence of undesirable vibration or noise due to imbalance.
Further related art is also disclosed in Japanese Patent Application Laid-open Nos. Hei-09-210418 and Sho-57-35198.